Methods and devices for facilitating emergency calls over wireless communication systems

ABSTRACT

One embodiment of the present disclosure relates to a method implemented by a first gateway node for processing an emergency call from an untrusted non-3GPP access network. The method comprises: receiving an emergency call request initiated from a terminal device over an untrusted non-3GPP based access network; detecting an event of the emergency call depending upon the emergency network access identifier included in the request message; selecting for the terminal device an emergency access point name that identifies an external network providing an emergency call service; and establishing for the terminal device an emergency call session with a second gateway node interfacing with the external network which is identified by the selected emergency access point name. According to an aspect of the present disclosure, there are provided corresponding methods and devices.

TECHNICAL FIELD

The present disclosure generally relates to wireless communication,particularly to methods and devices for facilitating emergency callsover an untrusted non-3GPP based access network.

BACKGROUND

This section is intended to provide a background to the variousembodiments of the invention that are described in this disclosure. Thedescription herein may include concepts that could be pursued, but arenot necessarily ones that have been previously conceived or pursued.Therefore, unless otherwise indicated herein, what is described in thissection is not prior art to the description and/or claims of thisdisclosure and is not admitted to be prior art by the mere inclusion inthis section.

Universal Mobile Telecommunications System (UMTS) is the 3rd Generation(3G) mobile communication system standardized by 3rd GenerationPartnership Project (3GPP). The 3GPP launched a study item known as“Long Term Evolution (LTE)”. The study will investigate means ofachieving major leaps in performance in order to improve serviceprovisioning, and to reduce user and operator costs. Out of that andbecause interworking with other radio access technologies should bepossible, the need arose for a new evolved Packet Core Network.

In general, in such mobile communication systems, a terminal device(also called User Equipment (UE)) has access to communication services(including basic services such as in particular providing IPconnectivity) via a network comprising a Core Network (CN) accessed byan Access Network (AN).

An example of 3GPP-based mobile communication system is Evolved PacketSystem (EPS), a description of which can be found in particular in 3GPPstandards such as for example 3GPP TS 23.401 and 3GPP TS 23.402 series.

According to the 3GPP standards, EPS includes Evolved Packet Core (EPC)that can be accessed by various access networks, including 3GPP basedaccess networks and non-3GPP based access networks. Examples of 3GPPbased access networks include UMTS Terrestrial Radio Access Network(UTRAN), evolved UTRAN (E-UTRAN), GSM EDGE Radio Access Network (GERAN),etc. Examples of non-3GPP based access networks include CDMA2000,Wireless Fidelity (WiFi) Access Network (specified by IEEE, inparticular in 802.11 specifications), Worldwide Interoperability forMicrowave Access (WiMAX) Access Network (specified by IEEE, inparticular in 802.16 specifications).

Two different types of non-3GPP based access networks are involved inthe 3GPP standards, i.e. untrusted non-3GPP based access networks andtrusted non-3GPP based access network, and normally whether a non-3GPPbased access network is trusted or not is left to specific 3GPPoperators. During initial attach or handover attach a UE needs todiscover the trust relationship (whether it is a trusted or untrustednon-3GPP access network) of the non-3GPP access network in order to knowwhich non-3GPP IP access procedure to initiate.

Some calling solutions enable mobile subscribers to make voice calls(initially) from an untrusted non-3GPP based access environment, such asfrom residential WiFi. The calls are managed by IP Multimedia Subsystem(IMS) Core, and the solution is sometimes referred to as Voice overWi-Fi. Those solutions also enable the user to maintain sessioncontinuity or IP address persistency when they handover between 3GPPbased access (such as for example LTE) to untrusted non-3GPP basedaccess (such as for example WiFi).

The procedures of non-3GPP Packet Date Network (PDN) connectionestablishment over untrusted non-3GPP access and the handover between3GPP based accesses and untrusted non-3GPP accesses are defined in 3GPPTS 23.402 and TS 23.401 series.

However, as to the emergency call service, the current 3GPP standards donot support emergency calls over an untrusted non-3GPP accesses (e.g.,WiFi) and emergency session continuity for the handover between a 3GPPbased access network and an untrusted non-3GPP based access network.Specifically, in the current 3GPP standard: IMS Emergency Session setupover untrusted non-3GPP based access (e.g., WiFi) is not supported; IMSEmergency Session Support for non-3GPP accesses connected to EPC islimited to support of handover of emergency sessions from E-UTRAN accessto High Rate Packet Date (HRPD) access (which is normally configured asa trusted access by operators); handover of IMS Emergency Sessions fromnon-3GPP access to 3GPP based access (e.g., E-UTRAN) is not supported.

SUMMARY

One or more method and apparatus embodiments according to the presentdisclosure aim to provide one or more solutions for facilitatingemergency calls over an untrusted non-3GPP based access network.

According to the first aspect of the present disclosure, there isprovided a method implemented by a first gateway node for processing anemergency call. The method comprises receiving an emergency call requestinitiated from a terminal device over an untrusted non-3GPP based accessnetwork. The emergency call request includes an emergency network accessidentifier constructed by the terminal device. The method furthercomprises detecting an event of the emergency call depending upon theemergency network access identifier; selecting for the terminal devicean emergency access point name that identifies an external networkproviding an emergency call service; and establishing for the terminaldevice an emergency call session with a second gateway node interfacingwith the external network which is identified with the selectedemergency access point name.

According to one or more embodiments of the first aspect of the presentdisclosure, the method further comprises informing the terminal deviceof the selected emergency access point name. In this way, the terminaldevice may store the emergency access point name so as to facilitatepotential handover from the untrusted non-3GPP based access network to a3GPP based access network.

According to the second aspect of the present disclosure, there isprovided a method implemented by a terminal device for initiating anemergency call over an untrusted non-3GPP based access network. Themethod comprises constructing an emergency network access identifier;sending to a first gateway node an emergency call request including theconstructed emergency network access identifier; and establishing, viathe first gateway node, an emergency call session with a second gatewaynode interfacing with an external network providing an emergency callservice.

According to one or more embodiments of the second aspect of the presentdisclosure, the method further comprises receiving from the firstgateway node an emergency access point name. In this way, the terminaldevice may then store the emergency access point name that identifiesthe external network providing the emergency call service, so as tofacilitate potential handover from the untrusted non-3GPP based accessnetwork to a 3GPP based access network.

According to the third aspect of the present disclosure, there isprovided a method implemented by a network node of a 3GPP based accessnetwork for facilitating emergency call handover from an untrustednon-3GPP based access network to the 3GPP based access network. Themethod comprises: receiving a request message sent from a terminaldevice that are currently performing an emergency call over theuntrusted non-3GPP based access network. The request message includes ahandover indication and an emergency access point name which identifiesan external network used to establish the emergency call. The methodfurther comprises: detecting an event of the emergency call handoverbased on the handover indication and the emergency access point name;establishing an emergency call session with a second gateway nodeinterfacing with the external network that is identified by the selectedemergency access point name; and switching the emergency call of theterminal device from bearer of the untrusted non-3GPP based accessnetwork to the bearer of the 3GPP based access network.

According to the fourth aspect of the present disclosure, there isprovided a method implemented by a network node of a 3GPP based accessnetwork for processing an emergency call. The method comprises:receiving an emergency call request initiated from a terminal deviceover a 3GPP based access network; selecting for the terminal device anemergency access point name that identifies an external networkproviding an emergency call service; establishing an emergency callsession with a second gateway node interfacing with the external networkthat is identified by the selected emergency access point name.

According to one or more embodiments of the fourth aspect of the presentdisclosure, the method further comprises informing the terminal deviceof the selected emergency access point name. In this way, the terminaldevice may store the emergency access point name that identifies theexternal network providing the emergency call service, so as tofacilitate potential handover from the untrusted non-3GPP based accessnetwork to a 3GPP based access network.

According to the fifth aspect of the present disclosure, there providesa method implemented by a first gateway node for facilitating emergencycall handover from a 3GPP based access network to an untrusted 3GPPbased access network. The method comprises receiving a request messagesent from a terminal device that is currently performing an emergencycall over the 3GPP based access network. The request message includes ahandover indication and an emergency access point name which identifiesan external network used to establish the emergency call. The methodfurther comprises: detecting an event of the emergency call handoverbased on the handover indication and the emergency network accessidentifier; and establishing an emergency call session with a secondgateway node interfacing with the external network that is identified bythe emergency access point name included in the request message.

According to the sixth aspect of the present disclosure, there providesa first gateway node operably for processing an emergency call. Thefirst gateway node comprises: a receiving unit configured to receive anemergency call request initiated from a terminal device over anuntrusted non-3GPP based access network. The emergency call requestincludes an emergency network access identifier constructed by theterminal device. The first gateway node further comprises a detectingunit configured to detect an event of the emergency call depending uponthe emergency network access identifier; a selecting unit configured toselect for the terminal device an emergency access point name thatidentifies an external network providing an emergency call service; anda session establishing unit configured to establish for the terminaldevice an emergency call session with a second gateway node interfacingwith the external network which is identified by the selected emergencyaccess point name.

According to the seventh aspect of the present disclosure, thereprovides a terminal device operably for initiating an emergency callover an untrusted non-3GPP based access network. The terminal devicecomprises: an identifier constructing unit configured to construct anemergency network access identifier; a transmitting unit configured tosend to a first gateway node an emergency call request including theconstructed emergency network access identifier; and a sessionestablishing unit configured to establish, via the first gateway node,an emergency call session with a second gateway node interfacing with anexternal network providing an emergency call service.

According to the eighth aspect of the present disclosure, there providesa network node of a 3GPP based access network operably for facilitatingemergency call handover from an untrusted non-3GPP based access networkto the 3GPP based access network. The network node comprises: areceiving unit configured to receive a request message sent from aterminal device that is currently performing an emergency call over theuntrusted non-3GPP based access network. The request message includes ahandover indication and an emergency access point name which identifiesan external network used to establish the emergency call. The networknode comprises: a detecting unit configured to detect an event of theemergency call handover based on the handover indication and theemergency access point name; a session establishing unit configured toestablish an emergency call session with a second gateway nodeinterfacing with the external network that is identified by the selectedemergency access point name; and a switching unit configured to switchthe emergency call of the terminal device from bearer of the untrustednon-3GPP based access network to the bearer of the 3GPP based accessnetwork.

According to the ninth aspect of the present disclosure, there providesa network node of a 3GPP based access network operably for processing anemergency call. The network node comprises: a receiving unit configuredto receive an emergency call request initiated from a terminal deviceover a 3GPP based access network; a selecting unit configured to selectfor the terminal device an emergency access point name that identifiesan external network providing an emergency call service; and a sessionestablishing unit configured to establish an emergency call session witha second gateway node interfacing with the external network that isidentified by the selected emergency access point name.

According to the tenth aspect of the present disclosure, there providesa first gateway node operably for facilitating emergency call handoverfrom a 3GPP based access network to an untrusted non-3GPP based accessnetwork. The first gateway node comprises: a receiving unit configuredto receive a request message sent from a terminal device that iscurrently performing an emergency call over the 3GPP based accessnetwork. The request message includes a handover indication and anemergency access point name which identifies an external network used toestablish the emergency call. The first gateway node further comprises:a detecting unit configured to detect an event of the emergency callhandover based on the handover indication and the emergency networkaccess identifier; and a session establishing unit configured toestablish an emergency call session with a second gateway nodeinterfacing with the external network that is identified by theemergency access point name included in the request message.

According to the eleventh aspect of the present disclosure, thereprovides a first gateway node operably for processing an emergency call.The first gateway node comprises processing means adapted to cause toreceive an emergency call request initiated from a terminal device overan untrusted non-3GPP based access network, wherein the emergency callrequest includes an emergency network access identifier constructed bythe terminal device; cause to detect an event of the emergency calldepending upon the emergency network access identifier; cause to selectfor the terminal device an emergency access point name that identifiesan external network providing an emergency call service; cause toestablish for the terminal device an emergency call session with asecond gateway node interfacing with the external network which isidentified by the selected emergency access point name.

According to the twelfth aspect of the present disclosure, thereprovides a terminal device operably for initiating an emergency callover an untrusted non-3GPP based access network. The terminal devicecomprises processing means adapted to: cause to construct an emergencynetwork access identifier; cause to send to a first gateway node anemergency call request including the constructed emergency networkaccess identifier; cause to establish, via the first gateway node, anemergency call session with a second gateway node interfacing with anexternal network providing an emergency call service.

According to the thirteenth aspect of the present disclosure, thereprovides a network node of a 3GPP based access network for facilitatingemergency call handover from an untrusted non-3GPP based access networkto the 3GPP based access network. The network node comprises processingmeans adapted to: cause to receive a request message sent from aterminal device that is currently performing an emergency call over theuntrusted non-3GPP based access network, wherein the request messageincludes a handover indication and an emergency access point name whichidentifies an external network used to establish the emergency call;cause to detect an event of the emergency call handover based on thehandover indication and the emergency access point name; cause toestablish an emergency call session with a second gateway nodeinterfacing with the external network that is identified by the selectedemergency access point name; cause to switch the emergency call of theterminal device from bearer of the untrusted non-3GPP based accessnetwork to the bearer of the 3GPP based access network.

According to the fourteenth aspect of the present disclosure, thereprovides a network node of a 3GPP based access network operably forprocessing an emergency call. The network node comprises processingmeans adapted to: cause to receive an emergency call request initiatedfrom a terminal device over a 3GPP based access network; cause to selectfor the terminal device an emergency access point name that identifiesan external network providing an emergency call service; cause toestablish an emergency call session with a second gateway nodeinterfacing with the external network that is identified by the selectedemergency access point name.

According to the fifteenth aspect of the present disclosure, thereprovides a first gateway node operably for facilitating emergency callhandover from a 3GPP based access network to an untrusted non-3GPP basedaccess network. The first gateway node comprises processing meansadapted to: cause to receive a request message sent from a terminaldevice that is currently performing an emergency call over the 3GPPbased access network, wherein the request message includes a handoverindication and an emergency access point name which identifies anexternal network used to establish the emergency call; cause to detectan event of the emergency call handover based on the handover indicationand the emergency network access identifier; cause to establish anemergency call session with a second gateway node interfacing with theexternal network that is identified by the emergency access point nameincluded in the request message.

According to one or more embodiments of the present disclosure, a useris allowed to make an emergency call even over an untrusted non-3GPPbased access network, for example, a WiFi residential environment. In ameanwhile, the continuity of the emergency call session can bemaintained by appropriately handing over between the untrusted non-3GPPbased access network and a 3GPP based access network.

BRIEF DESCRIPTION OF THE DRAWINGS

Inventive features regarded as the characteristics of the presentinvention are set forth in the appended claims. However, the presentinvention, its implementation mode, other objectives, features andadvantages will be better understood through reading the followingdetailed description on the exemplary embodiments with reference to theaccompanying drawings, where in the drawings:

FIG. 1 is a diagram schematically illustrating a network architecture,on which various embodiments of the present disclosure can be practiced;

FIG. 2 is a diagram schematically illustrating an exemplary flow chartof a method implemented by a first gateway node according to one or moreembodiments of the present disclosure;

FIG. 3 is a diagram schematically illustrating an exemplary flow chartof a method implemented by a terminal device according to one or moreembodiments of the present disclosure;

FIG. 4 is an example signaling diagram illustrating an embodiment wherean emergency call is initiated over an untrusted non-3GPP based accessnetwork;

FIG. 5 is a diagram schematically illustrating an exemplary flowchart ofa method implemented by a network node of a 3GPP based access networkaccording to one or more embodiments of the present disclosure;

FIG. 6 is an example signaling diagram illustrating an embodiment wherea handover of an emergency call is performed from an untrusted non-3GPPbased access network to a 3GPP based access network;

FIG. 7 is a diagram schematically illustrating an exemplary flowchart ofa method implemented by a network node of a 3GPP based access networkaccording to one or more embodiments of the present disclosure;

FIG. 8 is an example signaling diagram illustrating an embodiment wherean emergency call is initiated over a 3GPP based access network;

FIG. 9 is a diagram schematically illustrating an exemplary flow chartof a method implemented by a first gateway node according to one or moreembodiments of the present disclosure;

FIG. 10 is an example signaling diagram illustrating an embodiment wherea handover of an emergency call is performed from a 3GPP based accessnetwork to an untrusted non-3GPP based access network;

FIG. 11 is a schematic block diagram depicting a first gateway nodeoperably for processing an emergency call according to an embodiment ofthe present disclosure;

FIG. 12 is a schematic block diagram depicting a terminal deviceoperably for processing an emergency call according to an embodiment ofthe present disclosure;

FIG. 13 is a schematic block diagram depicting a 3GPP network nodeoperably for facilitating emergency call handover from an untrustednon-3GPP based access network to an 3GPP based access network accordingto an embodiment of the present disclosure;

FIG. 14 is a schematic block diagram depicting a 3GPP network nodeoperably for processing an emergency call according to an embodiment ofthe present disclosure;

FIG. 15 is a schematic block diagram depicting a first gateway nodeoperably for facilitating emergency call handover from a 3GPP basedaccess network to an untrusted non-3GPP based access network accordingto an embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be describedwith reference to the accompanying drawings. In the followingdescription, many specific details are illustrated so as to understandthe present disclosure more comprehensively. However, it is apparent tothe skilled in the art that implementation of the present invention maynot have these details. Additionally, it should be understood that thepresent invention is not limited to the particular embodiments asintroduced here. On the contrary, any combination of the followingfeatures and elements may be considered to implement and practice thepresent invention, regardless of whether they involve differentembodiments. For example, while it is described below in the context of5G cellular communication system for illustrative purposes, thoseskilled in the art will recognize that one or more embodiments of thepresent disclosure can also be applied to various other types ofcellular communication systems. Thus, the following aspects, features,embodiments and advantages are only for illustrative purposes, andshould not be understood as elements or limitations of the appendedclaims, unless otherwise explicitly specified in the claims.

FIG. 1 is a diagram schematically illustrating a network architecture,on which various embodiments of the present disclosure can be practiced.

As shown in FIG. 1, the system 100 is for example an EPS including anuntrusted non-3GPP based network 110 (e.g., a WiFi access network) and a3GPP based access network 130 (a LTE access network).

UE 120, which is attached to an access point (not shown) of theuntrusted non-3GPP access network 110, has an access to externalnetworks 170 (which provide IP services) via a first gateway node 140(e.g., an evolved Packet Data Gateway (ePDG)) and a second gateway node150 (e.g., a Packet Data Network Gateway (PDN Gateway, PGW)).

The first gateway node 140 interfaces with the untrusted nono-3GPP basedaccess network 110 enabling routing packet from/to the second gatewaynode 150 to/from UE 120 in the untrusted non-3GPP based access network110. The first gateway node 140 is also capable of relayingAuthentication, Authorization and Accounting (AAA) messages between theUE 120 and a 3GPP AAA server 180/Home Subscriber Server (HSS) 190 toperform 3GPP AAA procedures for the UE 120 in the untrusted non-3GPPbased access network 110. For implementation of the abovefunctionalities, different interfaces may be used by the first gatewaynode 140, as defined particular in 3GPP TS 23.402 v13.1.0:

-   -   S2b It provides the user plane with related control and mobility        support between the ePDG and the PGW;    -   SWn This is the reference point between the untrusted Non-3GPP        IP Access and the ePDG. Traffic on this interface for a        UE-initiated tunnel has to be forced towards the ePDG;    -   SWm This reference point is located between 3GPP AAA        Server/Proxy and the ePDG and is used for AAA signalling        (transport of mobility parameters, tunnel authentication and        authorization data).

The second gateway node 150 (e.g., a PGW of the EPS) providesconnectivity for UEs (in both the 3GPP based access network 130 and theuntrusted non-3GPP based access network 110) to the external packet datanetworks 170 by being the point of exit and entry of traffic for the UE.The second gateway node 150 is to act as the anchor for mobility between3GPP and non-3GPP technologies. For implementation of the abovefunctionalities, different interfaces may be used by the second gatewaynode 150, as defined particular in 3GPP TS 23.402 v13.1.0:

-   -   SGi It is the reference point between the PGW and the packet        data network (shown as “External networks 170” in FIG. 1).        Packet data network may be an operator external public or        private packet data network or an intra-operator packet data        network, e.g. for provision of IMS services.    -   S5 It provides user plane tunnelling and tunnel management        between the Serving GW (shown as “Serving Gateway 160” in        FIG. 1) and PGW. It is used for Serving GW relocation due to UE        mobility and in case the Serving GW needs to connect to a        non-collocated PDN GW for the required PDN connectivity.    -   S6b It is the reference point between PDN Gateway and 3GPP AAA        server/proxy (shown as “3GPP AAA server 180” in FIG. 1) for        mobility related authentication if needed. This reference point        may also be used to retrieve and request storage of mobility        parameters. This reference point may also be used to retrieve        static QoS profile for a UE for non-3GPP access in case dynamic        PCC is not supported.

The Serving Gateway (SGW) 160 routes and forwards user data packets,while also acting as the mobility anchor for the user plane duringinter-eNB handovers and as the anchor for mobility between LTE and other3GPP technologies.

Although not shown in FIG. 1, it should be appreciated by the personskilled in the art that the 3GPP based access network 130 comprisesdifferent functional network elements, for example, Node Bs (eNB oreNode B), Mobility Management Entities (MME).

The eNode B provides the E-UTRA user plane and control plane protocolterminations towards the UE in the 3GPP based access network 130.

The MME is the key control-node for the 3GPP based access network 130.It is responsible for idle mode UE tracking and paging procedureincluding retransmissions. It is involved in the beareractivation/deactivation process and is also responsible for choosing theSGW for UE at the initial attach and at time of intra-LTE handoverinvolving Core Network (CN) node relocation. It is responsible forauthenticating the user by interacting with the HSS 190. It checks theauthorization of the UE to camp on the service provider's Public LandMobile Network (PLMN) and enforces UE roaming restrictions.

A more detailed description of the network architecture can be found in3GPP TS 23.402 v13.1.0.

In the present disclosure, terminal devices also known as mobileterminals, wireless terminals and/or User Equipment (UE) are enabled tocommunicate wirelessly with a network node in a wireless communicationsystem, sometimes also referred to as a cellular radio system. Forinstance, a terminal device may include but is not limited to: mobilephone, smart phone, sensor device, meter, vehicle, household appliance,medical appliance, media player, camera, or any type of consumerelectronic, for instance, but not limited to, television, radio,lighting arrangement, tablet computer, laptop, or PC. The communicationdevice may be a portable, pocket-storable, hand-held,computer-comprised, or vehicle-mounted mobile device, enabled tocommunicate voice and/or data, via a wireless connection.

With reference to FIGS. 2-17, various embodiments of the presentdisclosure are described in details.

FIG. 2 is a diagram schematically illustrating an exemplary flow chartof a method 200 implemented by a first gateway node for processing anemergency call according to one or more embodiments of the presentdisclosure.

As shown in FIG. 2, the method 200 begins at step S210. In step S210,the first gateway node (e.g., the first gateway node 140) receives anemergency call request initiated from a terminal device (e.g., the UE120) over an untrusted non-3GPP based access network (e.g., theuntrusted non-3GPP based access network 110). In order to indicate theemergency call, the emergency call request includes an emergency networkaccess identifier constructed by the terminal device. Depending upon theemergency network access identifier (NAI) in the call request, the firstgateway node detects, in step S220, an event of the emergency call. Instep S230, an emergency access point name (APN) is selected by the firstgateway node, which identifies a particular external packet data network(one of the external networks 170) that provides the emergency callservice requested by the terminal device. The first gateway node thenestablishes, in step S240, for the terminal device an emergency callsession with a second gateway node (e.g., the second gateway node 150)interfacing with the external network which is identified by theselected emergency access point name.

In one or more embodiments of the present disclosure, the method 200 mayfurther comprises the following step (not shown in FIG. 1): the firstgateway node may inform the terminal device of the selected emergencyaccess point name. The terminal device may locally store the selectedaccess point name associated with the external network providing theemergency call service, thereby facilitating potential handoverprocedure from the untrusted non-3GPP based access network to a 3GPPbased access network, for example, due to its mobility.

According to one or more embodiments of the present disclosure, duringthe establishment of an emergency call session for the terminal device,the first gateway node may send to the second gateway node a createsession request including the selected emergency access point name,thereby enabling the second network node to identify the emergency callsession. Since the terminal device is communicatively interfacing withthe untrusted non-3GPP based environment, the first gateway node mayalso need to perform authentication procedure for the terminal devicebased on an equipment identity of the terminal device.

FIG. 3 is a diagram schematically illustrating an exemplary flow chartof a method 300 implemented by a terminal device for processing anemergency call according to one or more embodiments of the presentdisclosure.

As shown in FIG. 3, when initiating an emergency call over an untrustednon-3GPP based access network (e.g., the untrusted non-3GPP based accessnetwork 110), a terminal device (e.g., the UE 120) constructs, in stepS310, an emergency network access identifier for example in response toa user dialing an emergency number. The emergency network accessidentifier may include a predefined indicator of the emergency call, forexample, a character string “SOS”. In step S320, the terminal devicesends to a first gateway node (e.g., the first gateway node 140) anemergency call request including the constructed emergency networkaccess identifier.

An emergency call session with a second gateway node (e.g., the secondgateway node 150) is established via the first gateway node in stepS330. The second gateway node interfaces with an external network thatprovides the requested emergency call service.

According to one or more embodiments of the present disclosure, theterminal device may receive from the first gateway node an emergencyaccess point name and store it locally, thereby facilitating potentialhandover from the untrusted non-3GPP based access network to a 3GPPbased access network.

FIG. 4 is an example signaling diagram illustrating an embodiment wherean emergency call is initiated over an untrusted non-3GPP based accessnetwork.

As shown in FIG. 4, the UE communicates wirelessly with an access point(AP) of the untrusted non-3GPP based access network (for example, a WiFinetwork) and accesses to the external networks (e.g., public Internet,Intranet, operator's IMS networks). In the example of FIG. 4, the firstgateway node may be an ePDG and the second gateway node may be a PGW.

In step S401, the UE and the ePDG may exchange the first pair ofIKE_SA_INIT messages, in which the ePDG and the UE negotiatecryptographic algorithms, exchange nonces and perform a Diffie-Hellmanexchange, as specified in 3GPP TS 33.402 V12.5.0.

In step S402, the UE constructs an emergency network access identifier.The emergency network access identifier includes a predeterminedindicator of the emergency call and may be compliant to the definitionof 3GPP TS 23.003 series.

In step S403, the UE may send a request message IKE AUTH_REQ for theemergency call to the ePDG. The emergency network access identifierconstructed by the UE is included in the IKE_AUTH_REQ message. Moredetailed description of IKE AUTH_REQ is provided in Chapter 6.5 of 3GPPTS 33.402 series.

In some implementations, the UE may also include an emergency accesspoint name in the IKE AUTH_REQ, if it has been already configured by thenetwork.

In step S404, the ePDG detects depending upon the emergency networkaccess identifier that the current request is directed to an emergencycall. In some implementations, the ePDG may not treat the request as anemergency call request, if the ePDG only receives an emergency accesspoint name but without the emergency network access identifier from theUE.

In step S405, the ePDG may select an appropriate emergency access pointname for the UE, for example, by load balancing mechanism. The emergencyaccess point name identifies an external network which will provide theemergency call service for the UE.

In step S406, the ePDG may perform the local Extensible AuthenticationProtocol (EAP) authentication or the remote EAP authentication with anAAA server (not shown) based on UE Identity (e.g., International MobileEquipment Identity (IMEI) or International Mobile SubscriberIdentification Number (IMSI)) and configuration information. If the UEidentity is based on IMEI, then only local EAP authentication needs tobe performed.

In step S407, the UE may send the AUTH parameter to the ePDG.

In steps S408 and S409, the ePDG establishes for the UE an emergencycall session with the PGW that interfaces with the external networkidentified by the selected emergency access point name. Specifically,the ePDG may send (S408) a Create Session Request including the UE'sIMSI or IMEI, the emergency access point name to the PGW. Upon receiptof the Create Session Request, the PGW may detect the emergency callrequest based on the emergency APN included in the Request, then handleaccordingly and return (S409) a Create Session Response.

In step S410, the ePDG may send the selected emergency access point nameand other parameters received from the PGW (e.g., UE IP address) to theUE.

In step S411, the UE may locally store the selected emergency accesspoint name, so as to facilitate potential handover from the untrustednon-3GPP based access network to a 3GPP based access network.

FIG. 5 is a diagram schematically illustrating an exemplary flow chartof a method 500 implemented by a network node of a 3GPP based accessnetwork according to one or more embodiments of the present disclosure.

As shown in FIG. 5, the method 500 begins at step S510, where thenetwork node (e.g., MME) of the 3GPP based access network (e.g., the3GPP based access network 130) receives a request message (e.g., apacket data network connectivity request message or an attach requestmessage) sent from a terminal device (e.g., the UE 120) that iscurrently performing an emergency call over the untrusted non-3GPP basedaccess network (e.g., the untrusted non-3GPP based access network 110).The request message includes a handover indication and an emergencyaccess point name which identifies an external network (e.g., one of theexternal networks 170) used to establish the emergency call. The networknode detects in step S520 an event of the emergency call handover basedon the handover indication and the emergency access point name and thenestablishes in step S530 an emergency call session with a second gatewaynode (e.g., the second gateway node 150) interfacing with the externalnetwork that is identified by the selected emergency access point name.After the establishment of the emergency session with the second gatewaynode, the network node switches in step S540 the emergency call of theterminal device from the bearer of the untrusted non-3GPP based accessnetwork to the bearer of the 3GPP based access network.

According to one or more embodiments, during the establishment of theemergency call session with the second gateway node, the network nodemay send to the second gateway node a create session request includingthe emergency access point name, thereby enabling the second gatewaynode to identify the emergency call session.

FIG. 6 is an example signaling diagram illustrating an embodiment wherea handover of an emergency call is performed from an untrusted non-3GPPbased access network to a 3GPP based access network.

As shown in FIG. 6, the UE communicates wirelessly with an eNodeB of the3GPP based access network and accesses to the external networks (e.g.,public Internet, Intranet, operator's IMS networks). In the example ofFIG. 6, the network node of the 3GPP based access network mainlyhandling the emergency call handover procedure may be a MME; the firstgateway node may be an ePDG and the second gateway node may be a PGW.

In step S601, the UE may discover the 3GPP based access (e.g., E-UTRANaccess) and determine to transfer its emergency session from thecurrently used the untrusted non-3GPP based access network (e.g., WiFiaccess) to the 3GPP based access network. The UE sends an Attach Requestmessage or PDN Connectivity Request message to the MME with Request Typeindicating “Handover”. The UE also includes the related emergency accesspoint name in the request message, which was received from the ePDG instep S410 in FIG. 4. More detailed description of the message routedfrom the UE to the MME may be provided for example in 3GPP TS 23.401series.

In one or more embodiments of the present disclosure, if the UE isconnected to both the 3GPP based access network and the untrustednon-3GPP based access network before the emergency handover istriggered, the UE may set the “Request Type” as “Handover” and includethe relevant emergency access point name in a PDN Connectivity Requestmessage. If the UE is only connected to the untrusted non-3GPP basedaccess network before the emergency call handover is triggered, the UEmay set the “Attach Type” as “Emergency”, the “Request Type” to“Handover” and include the relevant emergency access point name in anAttach Request message.

In step S602, the MME detects that this is an emergency call handoverfrom the untrusted non-3GPP based access network depending upon the“emergency access point name” and the request type “Handover”, and thenselects the PGW associated with the emergency access point name includedin the request message.

According to one or more implementations of the present disclosure, toensure that the same right PGW can be selected in both 3GPP anduntrusted non-3GPP based access networks, the MME configuration maypreferably be consistent with the ePDG side, which means that one PGW isassociated with one emergency access point name. Multiple emergencyaccess point names may be configured to achieve load balancing amongmultiple PGWs and the PGW high availability.

In steps S603 and S604, the MME establishes an emergency call sessionwith the PGW that is connected with the external network identified bythe selected emergency access point name. Specifically, in step S603,the MME sends a Create Session Request message including the PGWaddress, the handover indication and the emergency access point name toa corresponding Serving gateway (SGW), which then forwards the CreateSession Request towards the selected PGW. The PGW may detect theemergency call handover from the untrusted non-3GPP based access networkdepending upon the “Handover Indication” and the “emergency access pointname” included in the Create Session Request message, then return (S604)a Create Session Response with the IP address of the UE. The SGW mayforward the Create Session Response message to the MME. This message mayalso serve as an indication to the MME that the S5 bearer setup has beensuccessful. The messaging among the MME, SGW and PGW for creating asession may be complaint with 3GPP TS 23.401 series.

From step S605 to step S608, the MME switches the emergency call of theUE from bearer of the untrusted non-3GPP based access network to thebearer of the 3GPP based access network. Specifically, in step S605,Radio and Access bearers are established in the 3GPP based accessnetwork, as specified in 3GPP TS 23.401 series. The MME may send in stepS606 a Modify Bearer Request message to the SGW, which includes eNodeBaddress, eNodeB TEID, and the Handover Indication. The SGW forwards theModify Bearer Request message to the PGW. The PGW may switch the datapath to the SGW, and then in step S607, return a Modify Bearer Response.The SGW may forward the Modify Bearer Response message to the MME. Instep S608, resource allocation deactivation procedure in the untrustednon-3GPP based access network may be initiated to delete the untrustednon-3GPP bearer.

FIG. 7 is a diagram schematically illustrating an exemplary flow chartof a method 700 implemented by a network node of a 3GPP based accessnetwork according to one or more embodiments of the present disclosure.

As shown in FIG. 7, the method 700 begins at step S710, where thenetwork node (e.g., a MME) receives an emergency call request initiatedfrom a terminal device (e.g., UE in the 3GPP based access network 130)over a 3GPP based access network (e.g., the 3GPP based access network130). In step S720, the network node selects for the terminal device anemergency access point name that identifies an external network (e.g.,one of the external networks 170) providing an emergency call service.The network node establishes, in step S730, an emergency call sessionwith a second gateway node (e.g., the second gateway 150) interfacingwith the external network that is identified by the selected emergencyaccess point name.

According to one or more embodiments of the present disclosure, thenetwork node may inform the terminal device of the selected emergencyaccess point name, thereby facilitating potential handover from the 3GPPbased access network to an untrusted non-3GPP based access network(e.g., the untrusted non-3GPP based access network 110).

FIG. 8 is an example signaling diagram illustrating an embodiment wherean emergency call is initiated over a 3GPP based access network.

As shown in FIG. 8, the UE may communicate wirelessly with an eNodeB ofthe 3GPP based access network and access to the external networks (e.g.,public Internet, Intranet, operator's IMS networks). In the example ofFIG. 8, the network node of the 3GPP based access network operablyprocessing an emergency call may be a MME; the first gateway node may bean ePDG and the second gateway node may be a PGW.

In step S801, the UE initiates the Attach procedure for an emergencycall by the transmission, to the eNodeB, of an Attach Request messagewith the “Attach Type” as “Emergency”. In some embodiments, an emergencyaccess point name may also be included in a PDN connectivity Requestmessage and sent to the MME.

In step S802, The MME may check if the user is allowed to performhandover to non-3GPP accesses, then for such an emergency call, anemergency access point name is selected which is associated with a PGW.

In steps S803 and S804, the MME establishes an emergency call sessionwith the PGW connected with the external network that is identified bythe selected emergency access point name. Specifically, the MME sends(S803) to a corresponding SGW a Create Session Request message includingthe emergency access point name, IMSI or IMEI of the UE, and the PGWaddress. The SGW may forward the Create Session Request message to thePGW. The PGW may detect the emergency call request depending upon theemergency access point name, handle accordingly, and return (S804) aCreate Session Response message with the IP address of the UE. Thismessage may also serve as an indication to the MME that the S5 bearersetup has been successful. The messaging among the MME, SGW and PGW forcreating a session may be complaint with the description of 3GPP TS23.401 series.

In step S805, radio and access bearers are established in the 3GPP basedaccess network, for example, as specified in TS 23.401. According to oneor more embodiments of the present disclosure, the selected emergencyaccess point name may be included in Activate Default EPS bearer Requestmessage to inform the UE.

In step S806, the MME may send a Modify Bearer Request message includingeNodeB address, eNodeB TEID to the SGW. The SGW acknowledges by sending,in step S807, Modify Bearer Response message including EPS BearerIdentity to the MME.

In step S809, the UE may store the related emergency access point namereceived in step 805 for potential use in following emergency handoverto the untrusted non-3GPP based access network.

FIG. 9 is a diagram schematically illustrating an exemplary flow chartof a method 900 implemented by a first gateway node according to one ormore embodiments of the present disclosure.

As shown in FIG. 9, the method 900 begins at step S910 where the firstgateway node (e.g., the first gateway node 110) receives a requestmessage sent from a terminal device (e.g., the UE 120) that is currentlyperforming an emergency call over the 3GPP based access network (130).The request message includes a handover indication and an emergencyaccess point name which identifies an external network (one of theexternal networks 170) used to establish the emergency call. In someimplementation, the request message may further include an emergencynetwork access identifier constructed by the terminal device. The firstgateway node detects, in step S920, an event of the emergency callhandover based on the handover indication and the emergency networkaccess identifier and then establishes, in step S930, an emergency callsession with a second gateway node (e.g., the second gateway node 150)interfacing with the external network that is identified by theemergency access point name included in the request message.

According to one or more embodiments of the present disclosure, duringthe establishment of the emergency call session, the first gateway nodemay send to the second gateway node a create session request includingthe handover indication and the emergency access point name, therebyenabling the second gateway node to identify the emergency call sessionand perform the emergency call handover. The first gateway node may alsoneed to perform authentication procedure for the terminal device basedon an equipment identity of the terminal device.

FIG. 10 is an example signaling diagram illustrating an embodiment wherea handover of an emergency call is performed from a 3GPP based accessnetwork to an untrusted non-3GPP based access network.

As shown in FIG. 10, the UE communicates wirelessly with an eNodeB ofthe 3GPP based access network and accesses to the external networks(e.g., public Internet, Intranet, operator's IMS networks) over the 3GPPbased access network (for example, a LTE network). In the example ofFIG. 10, the first gateway node may be an ePDG and the second gatewaynode may be a PGW.

In step S1001, the UE may discover the untrusted non-3GPP based accessnetwork (e.g., a WiFi network) and determine to handover its emergencycall session from the currently used 3GPP based access network to theuntrusted non-3GPP based access network. The UE and the ePDG mayexchange the first pair of IKE_SA_INIT messages, in which the ePDG andthe UE negotiate cryptographic algorithms, exchange nonces and perform aDiffie-Hellman exchange, for example, as specified in 3GPP TS 33.402V12.5.0.

In step S1002, the UE may send a request message IKE AUTH_REQ for thehandover of the emergency call to the ePDG. The emergency call handoverrequest includes a Handover Indication and the emergency access pointname the UE received, for example, at step S805 of FIG. 8. In someimplementations, according to the current standard, the UE may indicate“Handover” by including its preserved IP address in the IKE AUTH_REQmessage. Alternatively or additionally, the emergency call handoverrequest may further include an emergency network access identifier,which may include a predetermined indicator of the emergency call andmay be compliant with the definition of 3GPP TS 23.003 series.

In step S1003, the ePDG detects the emergency call handover requestdepending upon the emergency network access identifier and the handoverindication. The ePDG selects the corresponding PGW based on theemergency access point name included in the IKE AUTH_REQ message. TheePDG emergency APN configuration must be consistent with the ones in MMEto ensure the same PGW selected in the emergency handover between 3GPPand non-3GPP.

In step 1004, the ePDG may perform the local EAP authentication or theremote EAP authentication with an AAA server (not shown in FIG. 10)based on UE Identity (e.g., International Mobile Equipment Identity(IMEI) or International Mobile Subscriber Identification Number (IMSI))and configuration. For IMEI case, only local EAP authentication needs tobe performed.

In step S1005, the UE may send the AUTH parameter to the ePDG.

In steps S1006 and S1007, the ePDG establishes for the UE an emergencycall session with the PGW that interfaces with the external networkidentified by the emergency access point name included in the IKEAUTH_REQ message. Specifically, the ePDG may send (S1006) a CreateSession Request including the UE's IMSI or IMEI, the emergency accesspoint name and the handover indication to the PGW. Upon receipt of theCreate Session Request, the PGW may detect the emergency call handoverrequest from 3GPP based on the emergency access point name and thehandover indication, then handles accordingly and return (S1007) aCreate Session Response.

In step S1008, the ePDG may send the parameters received from PGW (e.g.,UE IP address) to the UE in an IKE AUTH RSP message.

FIG. 11 is a schematic block diagram depicting a first gateway node 1100operably for processing an emergency call according to an embodiment ofthe present disclosure.

As shown in FIG. 11, the first gateway node 1100 is configured toprocess an emergency call over an untrusted non-3GPP based accessnetwork. The first gateway 1100 comprises a receiving unit 1110, adetecting unit 1120, a selecting unit 1130 and a session establishingunit 1140. The first gateway node 1100 may comprise multiple suitablenetwork communications interfaces for communications with correspondingnetwork elements, as described with reference to FIG. 1.

The first gateway node 1100 comprises a processor 11, which may includeone or more microprocessor or microcontrollers, as well as other digitalhardware, which may include digital signal processors (DSPs),special-purpose digital logic, and the like. The processor 11 may beconfigured to execute program code stored in memory (not shown in FIG.11), which may include one or several types of memory such as read-onlymemory (ROM), random-access memory, cache memory, flash memory devices,optical storage devices, etc. Program code stored in memory includesprogram instructions for executing one or more telecommunications and/ordata communications protocols as well as instructions for carrying outone or more of the techniques described herein, in several embodiments.In some implementations, the processor 11 may be used to cause thereceiving unit 1110, the detecting unit 1120, the selecting unit 1130and the session establishing unit 1140 to perform correspondingfunctions according one or more embodiments of the present disclosure.

The receiving unit 1110 is configured to receive an emergency callrequest initiated from a terminal device over an untrusted non-3GPPbased access network. The emergency call request includes an emergencynetwork access identifier constructed by the terminal device. Thedetecting unit 1120 is configured to detect an event of the emergencycall depending upon the emergency network access identifier. Theselecting unit 1130 is configured to select for the terminal device anemergency access point name that identifies an external networkproviding an emergency call service. The session establishing unit 1140is configured to establish for the terminal device an emergency callsession with a second gateway node interfacing with the external networkwhich is identified by the emergency access point name selected by theselecting unit 1130.

According to one or more embodiments of the present disclosure, thefirst gateway node 1100 may further comprise a transmitting unit (notshown in FIG. 11) configured to inform the terminal device of theselected emergency access point name for following potential use ofhandover from the untrusted non-3GPP based access network to a 3GPPbased access network.

According to one or more embodiments of the present disclosure, thesession establishing unit 1140 may be further configured to send to thesecond gateway node a create session request including the selectedemergency access point name, thereby enabling the second network node toidentify the emergency call session. The session establishing unit 1140may be further configured to authenticate the terminal device based onan equipment identity of the terminal device.

FIG. 12 is a schematic block diagram depicting a terminal device 1200operably for processing an emergency call according to an embodiment ofthe present disclosure.

As shown in FIG. 12, the terminal device 1200 is configured to initiatean emergency call over an untrusted non-3GPP based access network. Theterminal device 1200 comprises: an identifier constructing unit 1210, atransmitting unit 1220, a session establishing unit 1230. The terminaldevice 1200 may also comprise multiple suitable radio frequencytransceivers (not shown in FIG. 12) that may be selectively coupled withone or more antenna(s) (not shown in FIG. 12) which are used to transmitsignals to, and receive signals from, other radio nodes such as aneNodeB or a WiFi AP.

The terminal device 1200 comprises a processor 12, which may include oneor more microprocessor or microcontrollers, as well as other digitalhardware, which may include digital signal processors (DSPs),special-purpose digital logic, and the like. The processor 12 may beconfigured to execute program code stored in memory (not shown in FIG.12), which may include one or several types of memory such as read-onlymemory (ROM), random-access memory, cache memory, flash memory devices,optical storage devices, etc. Program code stored in memory includesprogram instructions for executing one or more telecommunications and/ordata communications protocols as well as instructions for carrying outone or more of the techniques described herein, in several embodiments.In some implementations, the processor 12 may be used to cause theidentifier unit 1210, the transmitting unit 1220, the sessionestablishing unit 1230 to perform corresponding functions according oneor more embodiments of the present disclosure.

The identifier constructing unit 1210 is configured to construct anemergency network access identifier. According to one or moreembodiments of the present disclosure, the emergency network accessidentifier may include a predetermined indicator of the emergency call.The transmitting unit 1220 is configured to send to a first gateway nodean emergency call request including the constructed emergency networkaccess identifier. The session establishing unit 1230 is configured toestablish, via the first gateway node, an emergency call session with asecond gateway node interfacing with an external network providing anemergency call service.

According to one or more embodiments of the present disclosure, theterminal device 1200 may further comprise a receiving unit (not shown inFIG. 12) configured to receive from the first gateway node an emergencyaccess point name, thereby facilitating potential handover from theuntrusted non-3GPP based access network to a 3GPP based access network.

FIG. 13 is a schematic block diagram depicting a 3GPP network node 1300operably for facilitating emergency call handover from an untrustednon-3GPP based access network to the 3GPP based access network accordingto an embodiment of the present disclosure.

As shown in FIG. 13, the network node 1300 of a 3GPP based accessnetwork is configured to facilitate emergency call handover from anuntrusted non-3GPP based access network to the 3GPP based accessnetwork. The network node 1300 comprises a receiving unit 1310, adetecting unit 1320, a session establishing unit 1330, a switching unit1340. The network node 1300 may comprise multiple suitable networkcommunications interfaces for communications with corresponding networkelements, as described with reference to FIG. 1.

The network node 1300 comprises a processor 13, which may include one ormore microprocessor or microcontrollers, as well as other digitalhardware, which may include digital signal processors (DSPs),special-purpose digital logic, and the like. The processor 13 may beconfigured to execute program code stored in memory (not shown in FIG.13), which may include one or several types of memory such as read-onlymemory (ROM), random-access memory, cache memory, flash memory devices,optical storage devices, etc. Program code stored in memory includesprogram instructions for executing one or more telecommunications and/ordata communications protocols as well as instructions for carrying outone or more of the techniques described herein, in several embodiments.In some implementations, the processor 13 may be used to cause thereceiving unit 1310, the detecting unit 1320, the session establishingunit 1330 and the switching unit 1340 to perform corresponding functionsaccording one or more embodiments of the present disclosure.

The receiving unit 1310 is configured to receive a request message sentfrom a terminal device that is currently performing an emergency callover the untrusted non-3GPP based access network. The request messageincludes a handover indication and an emergency access point name whichidentifies an external network used to establish the emergency call.According to one or more embodiments of the present disclosure, therequest message may be a packet data network connectivity requestmessage or an attach request message. The detecting unit 1320 isconfigured to detect an event of the emergency call handover based onthe handover indication and the emergency access point name. The sessionestablishing unit 1330 is configured to establish an emergency callsession with a second gateway node interfacing with the external networkthat is identified by the selected emergency access point name. Theswitching unit 1340 is configured to switch the emergency call of theterminal device from bearer of the untrusted non-3GPP based accessnetwork to the bearer of the 3GPP based access network.

According to one or more embodiments of the present disclosure, thesession establishing unit 1330 may be further configured to send to thesecond gateway node a create session request including the emergencyaccess point name, thereby enabling the second gateway node to identifythe emergency call session.

FIG. 14 is a schematic block diagram depicting a 3GPP network node 1400operably for processing an emergency call according to an embodiment ofthe present disclosure.

As shown in FIG. 14, the network node 1400 is configured to process anemergency call over a 3GPP based access network. The network node 1400comprises a receiving unit 1410, a selecting unit 1420, a sessionestablishing unit 1430. The network node 1400 may comprise multiplesuitable network communications interfaces for communications withcorresponding network elements, as described with reference to FIG. 1.

The network node 1400 comprises a processor 14, which may include one ormore microprocessor or microcontrollers, as well as other digitalhardware, which may include digital signal processors (DSPs),special-purpose digital logic, and the like. The processor 14 may beconfigured to execute program code stored in memory (not shown in FIG.14), which may include one or several types of memory such as read-onlymemory (ROM), random-access memory, cache memory, flash memory devices,optical storage devices, etc. Program code stored in memory includesprogram instructions for executing one or more telecommunications and/ordata communications protocols as well as instructions for carrying outone or more of the techniques described herein, in several embodiments.In some implementations, the processor 14 may be used to cause thereceiving unit 1410, the selecting unit 1420, the session establishingunit 1430 to perform corresponding functions according one or moreembodiments of the present disclosure.

The receiving unit 1410 is configured to receive an emergency callrequest initiated from a terminal device over a 3GPP based accessnetwork. The selecting unit 1420 is configured to select for theterminal device an emergency access point name that identifies anexternal network providing an emergency call service; the sessionestablishing unit 1430 is configured to establish an emergency callsession with a second gateway node interfacing with the external networkthat is identified by the emergency access point name selected by theselecting unit 1420.

According to one or more embodiments of the present disclosure, thenetwork node 1400 may further comprise a transmitting unit configured toinform the terminal device of the selected emergency access point name.

FIG. 15 is a schematic block diagram depicting a first gateway node 1500operably for facilitating emergency call handover from a 3GPP basedaccess network to an untrusted non-3GPP based access network accordingto an embodiment of the present disclosure.

As shown in FIG. 15, the first gateway node 1500 is configured tofacilitate emergency call handover from a 3GPP based access network toan untrusted non-3GPP based access network. The first gateway 1500comprises a receiving unit 1510, a detecting unit 1520 and a sessionestablishing unit 1530. The first gateway node 1500 may comprisemultiple suitable network communications interfaces for communicationswith corresponding network elements, as described with reference to FIG.1.

The first gateway node 1500 comprises a processor 15, which may includeone or more microprocessor or microcontrollers, as well as other digitalhardware, which may include digital signal processors (DSPs),special-purpose digital logic, and the like. The processor 15 may beconfigured to execute program code stored in memory (not shown in FIG.15), which may include one or several types of memory such as read-onlymemory (ROM), random-access memory, cache memory, flash memory devices,optical storage devices, etc. Program code stored in memory includesprogram instructions for executing one or more telecommunications and/ordata communications protocols as well as instructions for carrying outone or more of the techniques described herein, in several embodiments.In some implementations, the processor 15 may be used to cause thereceiving unit 1510, the detecting unit 1520, and the sessionestablishing unit 1540 to perform corresponding functions according oneor more embodiments of the present disclosure.

The receiving unit 1510 is configured to receive a request message sentfrom a terminal device that is currently performing an emergency callover the 3GPP based access network. The request message includes ahandover indication and an emergency access point name which identifiesan external network used to establish the emergency call. According toone or more embodiments of the present disclosure, the request messagereceived by the receiving unit may further include an emergency networkaccess identifier constructed by the terminal device. The detecting unit1520 is configured to detect an event of the emergency call handoverbased on the handover indication and the emergency network accessidentifier. The session establishing unit 1530 is configured toestablish an emergency call session with a second gateway nodeinterfacing with the external network that is identified by theemergency access point name included in the request message.

According to one or more embodiments of the present disclosure, thesession establishing unit 1530 may be configured to send to the secondgateway node a create session request including the handover indicationand the emergency access point name, thereby enabling the second gatewaynode to identify the emergency call session and perform the emergencycall handover. The session establishing unit 1530 may be furtherconfigured to authenticate the terminal device based on an equipmentidentity of the terminal device.

According to one or more embodiments of the present disclosure, a useris allowed to make an emergency call even over an untrusted non-3GPPbased access network, for example, a WiFi residential environment. In ameanwhile, the continuity of the emergency call session can bemaintained by appropriately handing over between the untrusted non-3GPPbased access network and a 3GPP based access network.

In general, the various exemplary embodiments may be implemented inhardware or special purpose circuits, software, logical or anycombination thereof. For example, some aspects may be implemented inhardware, while other aspects may be implemented in firmware or softwarewhich may be executed by a controller, microprocessor or other computingdevice, although the disclosure is not limited thereto. While variousaspects of the exemplary embodiments of this disclosure may beillustrated and described as block and signaling diagrams, it is wellunderstood that these blocks, apparatus, systems, techniques or methodsdescribed herein may be implemented in, as non-limiting examples,hardware, software, firmware, special purpose circuits or logical,general purpose hardware or controller or other computing devices, orsome combination thereof.

As such, it should be appreciated that at least some aspects of theexemplary embodiments of the disclosure may be practiced in variouscomponents such as integrated circuit chips and modules. As well knownin the art, the design of integrated circuits is by and large a highlyautomated process.

The present disclosure may also be embodied in the computer programproduct which comprises all features capable of implementing the methodas depicted herein and may implement the method when loaded to thecomputer system.

The present disclosure has been specifically illustrated and explainedwith reference to the preferred embodiments. The skilled in the artshould understand various changes thereto in form and details may bemade without departing from the spirit and scope of the presentdisclosure.

1. A method implemented by a first gateway node for processing anemergency call, comprising: receiving an emergency call requestinitiated from a terminal device over an untrusted non-3GPP based accessnetwork, wherein the emergency call request includes an emergencynetwork access identifier constructed by the terminal device; detectingan event of the emergency call depending upon the emergency networkaccess identifier; selecting for the terminal device an emergency accesspoint name that identifies an external network providing an emergencycall service; and establishing for the terminal device an emergency callsession with a second gateway node interfacing with the external networkwhich is identified by the selected emergency access point name.
 2. Themethod according to claim 1, further comprising informing the terminaldevice of the selected emergency access point name, thereby facilitatingpotential handover from the untrusted non-3GPP based access network to a3GPP based access network.
 3. The method according to claim 1, whereinestablishing an emergency call session for the terminal devicecomprises: sending to the second gateway node a create session requestincluding the selected emergency access point name, thereby enabling thesecond network node to identify the emergency call session.
 4. Themethod according to claim 1, wherein establishing an emergency callsession for the terminal device comprises: authenticating the terminaldevice based on an equipment identity of the terminal device.
 5. Amethod implemented by a terminal device for initiating an emergency callover an untrusted non-3GPP based access network, comprising:constructing an emergency network access identifier; sending to a firstgateway node an emergency call request including the constructedemergency network access identifier; and establishing, via the firstgateway node, an emergency call session with a second gateway nodeinterfacing with an external network providing an emergency callservice.
 6. The method according to claim 5, wherein the emergencynetwork access identifier includes a predetermined indicator of theemergency call.
 7. The method according to claim 5, further comprising:receiving from the first gateway node an emergency access point name,thereby facilitating potential handover from the untrusted non-3GPPbased access network to a 3GPP based access network.
 8. A methodimplemented by a network node of a 3GPP based access network forfacilitating emergency call handover from an untrusted non-3GPP basedaccess network to the 3GPP based access network, comprising: receiving arequest message sent from a terminal device that is currently performingan emergency call over the untrusted non-3GPP based access network,wherein the request message includes a handover indication and anemergency access point name which identifies an external network used toestablish the emergency call; detecting an event of the emergency callhandover based on the handover indication and the emergency access pointname; establishing an emergency call session with a second gateway nodeinterfacing with the external network that is identified by the selectedemergency access point name; and switching the emergency call of theterminal device from a bearer of the untrusted non-3GPP based accessnetwork to the to a bearer of the 3GPP based access network.
 9. Themethod according to claim 8, wherein the request message is a packetdata network connectivity request message or an attach request message.10. The method according to claim 8, wherein establishing an emergencycall session with a second gateway node comprises: sending to the secondgateway node a create session request including the emergency accesspoint name, thereby enabling the second gateway node to identify theemergency call session.
 11. A method implemented by a network node of a3GPP based access network for processing an emergency call, comprising:receiving an emergency call request initiated from a terminal deviceover a 3GPP based access network; selecting for the terminal device anemergency access point name that identifies an external networkproviding an emergency call service; and establishing an emergency callsession with a second gateway node interfacing with the external networkthat is identified by the selected emergency access point name.
 12. Themethod according to claim 11, further comprising: informing the terminaldevice of the selected emergency access point name, thereby facilitatingpotential handover from the 3GPP based access network to an untrustednon-3GPP based access network.
 13. A method implemented by a firstgateway node for facilitating emergency call handover from a 3GPP basedaccess network to an untrusted 3GPP based access network, comprising:receiving a request message sent from a terminal device that iscurrently performing an emergency call over the 3GPP based accessnetwork, wherein the request message includes a handover indication andan emergency access point name which identifies an external network usedto establish the emergency call; detecting an event of the emergencycall handover based on the handover indication and the emergency networkaccess identifier; and establishing an emergency call session with asecond gateway node interfacing with the external network that isidentified by the emergency access point name included in the requestmessage.
 14. The method according to claim 13, wherein establishing anemergency call session for the terminal device comprises: sending to thesecond gateway node a create session request including the handoverindication and the emergency access point name, thereby enabling thesecond gateway node to identify the emergency call session and performthe emergency call handover.
 15. The method according to claim 13,wherein establishing an emergency call session for the terminal devicecomprises: authenticating the terminal device based on an equipmentidentity of the terminal device.
 16. The method according to claim 13,wherein the request message further includes an emergency network accessidentifier constructed by the terminal device.
 17. A first gateway nodeoperably for processing an emergency call, comprising: a receiving unitconfigured to receive an emergency call request initiated from aterminal device over an untrusted non-3GPP based access network, whereinthe emergency call request includes an emergency network accessidentifier constructed by the terminal device; a detecting unitconfigured to detect an event of the emergency call depending upon theemergency network access identifier; a selecting unit configured toselect for the terminal device an emergency access point name thatidentifies an external network providing an emergency call service; anda session establishing unit configured to establish for the terminaldevice an emergency call session with a second gateway node interfacingwith the external network which is identified by the selected emergencyaccess point name.
 18. The first gateway node according to claim 17,further comprising: a transmitting unit configured to inform theterminal device of the selected emergency access point name, therebyfacilitating potential handover from the untrusted non-3GPP based accessnetwork to a 3GPP based access network.
 19. The first gateway nodeaccording to claim 17, wherein the session establishing unit is furtherconfigured to send to the second gateway node a create session requestincluding the selected emergency access point name, thereby enabling thesecond network node to identify the emergency call session.
 20. Thefirst gateway node according to claim 17, wherein the sessionestablishing unit is further configured to authenticate the terminaldevice based on an equipment identity of the terminal device.
 21. Aterminal device operably for initiating an emergency call over anuntrusted non-3GPP based access network, comprising: an identifierconstructing unit configured to construct an emergency network accessidentifier; a transmitting unit configured to send to a first gatewaynode an emergency call request including the constructed emergencynetwork access identifier; and a session establishing unit configured toestablish, via the first gateway node, an emergency call session with asecond gateway node interfacing with an external network providing anemergency call service.
 22. The terminal device according to claim 21,wherein the emergency network access identifier includes a predeterminedindicator of the emergency call.
 23. The terminal device according toclaim 21, further comprising: a receiving unit configured to receivefrom the first gateway node an emergency access point name, therebyfacilitating potential handover from the untrusted non-3GPP based accessnetwork to a 3GPP based access network.
 24. A network node of a 3GPPbased access network operably for facilitating emergency call handoverfrom an untrusted non-3GPP based access network to the 3GPP based accessnetwork, comprising: a receiving unit configured to receive a requestmessage sent from a terminal device that is currently performing anemergency call over the untrusted non-3GPP based access network, whereinthe request message includes a handover indication and an emergencyaccess point name which identifies an external network used to establishthe emergency call; a detecting unit configured to detect an event ofthe emergency call handover based on the handover indication and theemergency access point name; a session establishing unit configured toestablish an emergency call session with a second gateway nodeinterfacing with the external network that is identified by the selectedemergency access point name; and a switching unit configured to switchthe emergency call of the terminal device from a bearer of the untrustednon-3GPP based access network to a bearer of the 3GPP based accessnetwork.
 25. The network node according to claim 24, wherein the requestmessage is a packet data network connectivity request message or anattach request message.
 26. The network node according to claim 24,wherein the session establishing unit is further configured to send tothe second gateway node a create session request including the emergencyaccess point name, thereby enabling the second gateway node to identifythe emergency call session.
 27. A network node of a 3GPP based accessnetwork operably for processing an emergency call, comprising: areceiving unit configured to receive an emergency call request initiatedfrom a terminal device over a 3GPP based access network; a selectingunit configured to select for the terminal device an emergency accesspoint name that identifies an external network providing an emergencycall service; and a session establishing unit configured to establish anemergency call session with a second gateway node interfacing with theexternal network that is identified by the selected emergency accesspoint name.
 28. The network node according to claim 27, furthercomprising: a transmitting unit configured to inform the terminal deviceof the selected emergency access point name, thereby facilitatingpotential handover from the 3GPP based access network to an untrustednon-3GPP based access network.
 29. A first gateway node operably forfacilitating emergency call handover from a 3GPP based access network toan untrusted non-3GPP based access network, comprising: a receiving unitconfigured to receive a request message sent from a terminal device thatis currently performing an emergency call over the 3GPP based accessnetwork, wherein the request message includes a handover indication andan emergency access point name which identifies an external network usedto establish the emergency call; a detecting unit configured to detectan event of the emergency call handover based on the handover indicationand the emergency network access identifier; and a session establishingunit configured to establish an emergency call session with a secondgateway node interfacing with the external network that is identified bythe emergency access point name included in the request message.
 30. Thefirst gateway node according to claim 29, wherein the sessionestablishing unit is configured to send to the second gateway node acreate session request including the handover indication and theemergency access point name, thereby enabling the second gateway node toidentify the emergency call session and perform the emergency callhandover.
 31. The first gateway node according to claim 29, wherein thesession establishing unit is further configured to authenticate theterminal device based on an equipment identity of the terminal device.32. The first gateway node according to claim 29, wherein the requestmessage received by the receiving unit further includes an emergencynetwork access identifier constructed by the terminal device.
 33. Afirst gateway node operably for processing an emergency call, comprisinga processor adapted to: cause to receive an emergency call requestinitiated from a terminal device over an untrusted non-3GPP based accessnetwork, wherein the emergency call request includes an emergencynetwork access identifier constructed by the terminal device; cause todetect an event of the emergency call depending upon the emergencynetwork access identifier; cause to select for the terminal device anemergency access point name that identifies an external networkproviding an emergency call service; and cause to establish for theterminal device an emergency call session with a second gateway nodeinterfacing with the external network which is identified by theselected emergency access point name.
 34. The first gateway nodeaccording to claim 33, further comprising a memory, wherein the memoryincludes instructions executable by the processor.
 35. A terminal deviceoperably for initiating an emergency call over an untrusted non-3GPPbased access network, comprising a processor adapted to: cause toconstruct an emergency network access identifier; cause to send to afirst gateway node an emergency call request including the constructedemergency network access identifier; and cause to establish, via thefirst gateway node, an emergency call session with a second gateway nodeinterfacing with an external network providing an emergency callservice.
 36. The terminal device node according to claim 35, furthercomprising a memory, wherein the memory includes instructions executableby the processor.
 37. A network node of a 3GPP based access network forfacilitating emergency call handover from an untrusted non-3GPP basedaccess network to the 3GPP based access network, a processor adapted to:cause to receive a request message sent from a terminal device that iscurrently performing an emergency call over the untrusted non-3GPP basedaccess network, wherein the request message includes a handoverindication and an emergency access point name which identifies anexternal network used to establish the emergency call; cause to detectan event of the emergency call handover based on the handover indicationand the emergency access point name; cause to establish an emergencycall session with a second gateway node interfacing with the externalnetwork that is identified by the selected emergency access point name;and cause to switch the emergency call of the terminal device frombearer of the untrusted non-3GPP based access network to the bearer ofthe 3GPP based access network.
 38. The network node according to claim33, further comprising a memory, wherein the memory includesinstructions executable by the processor.
 39. A network node of a 3GPPbased access network operably for processing an emergency call,comprising a processor adapted to: cause to receive an emergency callrequest initiated from a terminal device over a 3GPP based accessnetwork; cause to select for the terminal device an emergency accesspoint name that identifies an external network providing an emergencycall service; and cause to establish an emergency call session with asecond gateway node interfacing with the external network that isidentified by the selected emergency access point name.
 40. The networknode according to claim 39, further comprising a memory, wherein thememory includes instructions executable by the processor.
 41. A firstgateway node operably for facilitating emergency call handover from a3GPP based access network to an untrusted non-3GPP based access network,comprising a processor adapted to: cause to receive a request messagesent from a terminal device that is currently performing an emergencycall over the 3GPP based access network, wherein the request messageincludes a handover indication and an emergency access point name whichidentifies an external network used to establish the emergency call;cause to detect an event of the emergency call handover based on thehandover indication and the emergency network access identifier; andcause to establish an emergency call session with a second gateway nodeinterfacing with the external network that is identified by theemergency access point name included in the request message.
 42. Thefirst gateway node according to claim 41, further comprising a memory,wherein the memory includes instructions executable by the processor.